Circuit breaker



Oct. 17, 1961 D. B. POWELL 3,005,066

cmcurw BREAKER Original Filed Dec. 19, 1958 4 Sheets-Sheet 1 IN VEN TORDAVID B. Powzu. BY MQ ATTORNEY D. B. POWELL CIRCUIT BREAKER Oct. 17,1961 4 Sheets-Sheet 2 Original Filed Dec. 19, 1958 INVENTOR I 6 DAVID B.PQQELL Oct. 17, 1961 D. B. POWELL 3,005,066

CIRCUIT BREAKER Original Filed Dec. 19, 1958 4 Sheets-Sheet 3 IN V ENTOR ATTORNEY D. B. POWELL CIRCUIT BREAKER Oct. 17, 1961 4 Sheets-Sheet 4Original Filed Dec. 19, 1958 FIG. IO

FIG. 5A

IN V EN TOR DAVID B. Powsu. BY RM] 7 ATTORNEY United States PatentO3,005,066 CIRCUIT BREAKER David Barton Powell,Bristol, Conn zassignor.to General Electric Company, .acorporation of New-York Originalapplication Dec. 19, 1958, Ser. No. 781,766. -Divided and thisapplication .Oct. 1.0,. 1960, Ser. No. 61,719

Claims. (Cl. 200---78) My invention relates to electric circuit breakersand particularly to electric circuit breakers ofthe type includingmovable contacts operated by an overcentenspring type operatingmechanism and enclosed in a casing of molded insulating material andsuitable for use in industrial and commercialapplications. Thisapplicationis a division of our co-pending application Serial Number781,766, filed December 19,1958, and assigned to the same assignee asthe present invention.

The increasing volume and complexity of electrical apparatus for thecontrol and protection of electric circuitsin industry has createdacontinuing-need for reduction in the size, and converselyan increase inthe electrical rating or capacity of such apparatus, andpartic- I ularlyof electric circuit breakers used for the control and protection ofelectric power circuits.

Since electric circuit breakers are commonly used in assembliescomprising a substantial number of such circuit'breakers, bymanufacturers of various types of assemblies of electrical equipment,such assemblies, have, over the years, become standardized withcertainmounting spaces available and with a certain dimensional modulusprovided for circuit breakers. Likewise, electrical ratings of circuitbreakers have, by custom, become established in certain predeterminedsteps of voltage and current. Thus, for example, .circuit breakers areused in onegeneral class of applications with voltage ratings of 110-125volts, in another class of applicationsat 240 volts and in still anotherlarge'class of v l-' plicationsat 480 and600 volts. The ampere ratingsof such circuit breakers are similarly commonly provided for, in termsof safety code regulations, etc in steps suchas '10, 15, 20, 30,50, 100amperes, etc.

For these reasons, it is notpossible to increase the rating or decreasethe .size of such industrial circuit breakers in convenient, smallsteps. Instead, the rating of a particular circuit breaker if increasedat all, must he jumped .to that of the next largest commonly used ratingor, conversely, the size of a circuit breakerlmust be reduced tothatofthe next smallest commonly used circuit breaker. p

Accordingly, it is a general object of the presentin vention to providean industrialtype circuit breaker having the physical dimensions of onetype of commonly used priorart circuit breaker, for-example, a'.125volt, I

50 ampere circuit breaker, with a 5,000 ampere interrupting rating,which breaker also'has the electrical-current carrying and interruptingcapacities ofv the next largest ,siZe circuit breaker, evenithoughsuchnextlargest size has a voltage rating'four to five times as greatandashort circuit interrupting capacity at'least double, such, for example,as 480. or .600 volt, 100-.an 1pere circuit breaker having a.10,000,amperes'interrupting rating.

The higher voltage rating of such breakers requires that the mechanismand the associatedparts including the terminals and insulating parts berelatively compact and spaced at proper distances to provide therequired oversurtace electrical clearance of increasedamount as requiredby the higher voltage. Theincreased short circuit interrupting capacityrequires the use of refractory type contacts, Which,in turn, requiresrelatively higher contact pressure in order to maintain requiredlowcontact resistance. This, inturn, requires the provision-of anoperating mechanism capableof exerting a contact 2 pressuresubstantially in excess of the prior art type breaker. In addition, suchcircuit breakermust-be'provided with a construction which canbe readilymanufactured and assembled and sold at relatively lowcost.

' All of these, overlapping and seemingly incompatible requirements mustbe 'met in order to provide a circuit breaker of such increased rating.i 1

Accordingly, it is an objectof the present invention to provide anelectric circuit breaker including an operating mechanism capable ofexertingrelativelyhigh contact pressures and occupying a space nogreater than Prior art breakers of substantially lower rating.

It is another object of the invention to provide a circuit breakermechanism including mechanism side plates which are separatelyfabricated and joined together to support the mechanism-therebetween,which require only a single joining means and the side plates of whichare held in their relatively predetermined desired positions by meanswhich also mount them to the insulating base of the circuit breaker.

It is a further object of the invention to providea circuitbreakerincluding a molded insulating casing which does not require theuse ofmolded-in metallic inserts to fasten or mount the. parts. I Inaccordance withthe invention in one form, an electrio-circuit breaker isprovided including an insulating casing containing a plurality of gaugedcontacts and operatingmechanism for operatingthe contacts between openand closedf positions The operating mechanism includes two opposed sideframes, each having a returnbent portion. A releasable trip member ispivotally supported between the return-bent portions, providing .anextremely rigid, yet simple, construction.

In accordance with another aspect of theinvention, each of thev side.plates has its lower edge portion in engagement with a bottom surfaceof'the insulating casing and has portions thereof lanced out anddeformedto opposite sides of its general plane. "Retaining screws hold.the side plates. against the insulating base. This retainsthe sideplatesinvexact alignment with Eeachothcr, as required by the mechanism.

Other objects. and advantages ofthe, invention .will, in part, bepointed outand, in part, become obvious from the followin detaileddescription. and the scope offthe invention will be pointed outparticularly in the. appended claims.

.In the drawings,

. FIGURE 1 is a top plan view ofamultipolecircuit breaker incorporatingthe invention, a, portion. of the casing being broken away; I i i FIGURE2 is a sideelevationview partially in section taken generally on theline 2-2 of FIGUREl. and .show ing the primary current, path throughcnepole. of-the circuit breaker;

FIGURE 3 is a side elevation viewof theroperating mechanism,'partiallyin. section; i

FIGURE 4. is a sideelevation view of the operating mechanism, the partsbeing shown in automatically openedtor ftripped.c0nditi0n;

FIGURE SyiS-Q. fragmentary sectional view,-- on...cnlarged scale,.showingthe details-of. mounting of,the:mechanism sideframes in theinsulating casing;

FIGURE 5a ,is .a fragmentary sectional VICWwOfHthG operating mechanismof the circuit breaker;

FIGURE 6.is a'fragmentary elevation view ofaportion of "the mechanismofa modifiedform of the invention adapted for usein asin'gle-pole circuitbreaker;

FIGURE 7 is an; exploded perspective viewof the-current responsivetripping mechanism parts of the circuit breaker-of FIGURE =1; g

FIGURES 8 and'9 are perspective vieWs-ofcurrentmsponsive trippingmechanism of modified forms of the invention;

FIGURE is a top plan view of a portion of the circuit breaker of FIGURE1 showing an auxiliary or trip alarm switch in position.

In the drawings, the invention is shown in FIGURE 1 as incorporated in athree-pole electric circuit breaker comprising an insulating casingincluding an insulating base portion 10 and an insulating cover portion11. The base portion 10 includes three elongated side-by-side recesses12, only one shown, each having a relatively stationary contact 13mounted therein on a terminal strap 14 which, in turn, is connected to aline terminal 15, positioned in a recess located at one end of thecircuit breaker. A relatively movable contact 16 is also provided ineach of the chambers 12 and is carried by a two-part contact armcomprising a contact-carrying portion 17 and a mounting portion 18 whichare pivotally interconnected by pivot pin 19. The contact-carryingportion 17 is biased for rotation about the pivot pin 19 with respect tothe mounting portion 18 by means of a compression spring 20, and suchrotation is limited in the clockwise direction by the engagement of thecontact-carrying portion 17 with an upwardly bent stop portion 21carried by the mounting portion 18.

For the purpose of assisting in extinguishing arcs, each chamber 12 isprovided with a series of spaced notched plates 13a, and a generallyV-shaped grid 13b, through which are gases are forced to pass inescaping. The grids 13b are formed of relatively thick sheet metalhaving a plurality of closely spaced holes therein.

The mounting portion 18 of the contact arm is generally U-shaped and hasaligned generally square openings in the opposite sides thereof adjacentthe bight, through which a common contact cross arm 22 extends, havingan enlarged hub portion of generally square cross section and a metallicreinforcing core 23. The portion 18 is attached firmlyto the contactcross arm 22 by means of a generally U-shaped fastening member 24 whichextends around the contact cross arm and has its ends bent extendingthrough and bent over the bight portion of the member 18.

Clockwise rotation of the contact cross arm 22 therefore causesclockwise rotation of the contact arm assembly and engagement of themovable contact 16 with the stationary contact 13. Following initialengagement of these contacts slight further rotation of the contactcross arm takes place causing slight compression of the spring 20,providing dependable contact pressure.

The contact-carrying portion 17 of the contact arms are each connectedby a flexible conductor or braid 25 to a connecting strap 26, which inturn is connected to a relatively rigid magnet winding conductor 27encircling a magnet core member 28 and having its other end connected tothe lower end of an elongated bimetallic strip member 29, which in turnis anchored to the insulating casing by suitable means such as by screw30.

The upper end of the bimetallic strip 29 is connected by a flexibleconductor or braid 31 to a terminal strap 32 which in turn is fixedlyattached to a load terminal member 33 positioned in a recess at the loadend of the circuit breaker.

The primary current path through the circuit breaker, when the contactsare in the closed circuit position, through one pole thereof, istherefore as follows, beginning with the load terminal 33: from loadterminal 33 to conductive strap 32, to flexible conductor 31, throughbimetallic strip 29, to magnet winding 27, to connecting strap 26, toflexible conductor 25, to contact-carrying member 17, to movable contact16, to stationary contact 13, to connecting terminal strap 14, to lineterminal 15.

The magnet core 28 has two irregularly shaped pole pieces 34 fixedlyattached to the opposite ends thereof. A relatively movable armature 35is also provided, com- .prisinga member formed out of relatively thinsheet metal material and pivotally supported by engagement of theshoulders 36 thereof which rest upon corresponding shoulders or ledgesin the insulating casing of the base 10. The armature member 35 has anupstanding portion 37 for purposes described, an intermediate offsetportion, and a depending relatively wide portion 38 which is adapted tobe attracted to the pole face portions 34 ot' the magnet to causetripping in a manner to be described.

The armature member 35 is biased for rotation, counterclockwise by meansof an elongated leaf-type spring (see FIGURE 1, omitted from FIGURE 2for clarity) 39 which is rigidly attached to the armature 35 at a pointjust above the pivot point 36 and which has its lower end extending intoengagement with a side ledge portion of the side wall of the insulatingcasing. The action of the spring 39 is such as to resist movement of thearmature member in a clockwise direction and to normally retain it inengagement with a stop surface 40 integral with the insulating casing.

The armature member 35 is therefore supported simply by resting ininsulating bearings in the side walls of each chamber and its normalposition is determined by insulating surfaces 40 provided in theinsulating casing by molding. The normal position of the armature istherefore very closely controlled by the molded-in dimensions of theinsulating casing.

In order to protect the bimetallic strip from being adversely affectedby short circuit currents, a bypassing circuit is provided comprising aflexible conductor or braid 41 having one end thereof attached to theupper end of the bimetallic strip 29 and having its other end connectedto an intermediate portion of the armature 35. A contact 42 is alsoprovided on the armature 35 adapted to coact with a contact 43 mountedon a conducting strap 44 connected to the flexible conductor 25 by meansof screw 45.

On the occurrence of high short-circuit currents, the armature member 35is attracted toward the pole members 34 and the contact 42 touches thecontact 43. At this ime, therefore, a bypassing circuit is establishedwhich shunts the greater portion of such short-circuit current aroundthe bimetallic strip 29 and the magnet 28, directly to the braid 25 andthe movable contact.

For the purpose of operating the contact cross arm 22 and its associatedcontact arm assemblies between open and closed circuit positionsmanually as desired and automatically upon the occurrence ofpredetermined current conditions in the circuit through such contacts,an operating mechanism is provided, as shown particularly at FIGURES 35.The mechanism comprises a pair of opposed side plates 50 and 51, seeFIGURE 5, which are generally planar throughout the major portionthereof but have the right-hand portion as viewed return-bent to form aU-shaped section as shown particularly at FIGURE 5a. The return-bentportions 52 and 53 are spaced apart a short distance to receive areleasable trip member 54 and the parts having aligned openings thereinthrough which a pivot pin 55 extends. The pivot pin 55 has its oppositeends headed over to attach these parts permanently together at thispoint. The return-bent portions 53 each also include a projection 56 fora purpose to be described.

The operating mechanism includes a pair of interconnected toggle links57 and 58, pivotally connected respectively to the releasable tripmember at 59 and to the center contact arm assembly at 60, the pivot pin60 being the same pivot pin which interconnects the two portions of thecenter contact arm.

The releasable trip member 54 includes a latching projection 61 which isnormally in engagement with a bent-over portion 62 of an intermediatelatch member 63, pivotally supported between the side walls of themechanism on pin 64. The latch member 63 has a lower extension portion65 for resetting purposes in a manner to be described. The intermediatelatch member 63 is normally :be observed from FIGURE 3 and FIGURE 4.FIGURE .3, the circuit breaker mechanism is shown in held in theposition shown-in-FIGURE 3 by theengage theedge oftheportion 62 by.projectingainto an opening 70 in the latchmember 63.

It will therefore be observed that upwardor clockwise rotation forceiotthe releasabletrip. member54 exertsa counterclockwise bias on theintermediate latch member 63. The latch member 63 is preventedfromrotating in a counterclockwise:direction, however, by itsvengagementwithzthe porti-on 69 of the latchmember 66.

The toggle members57 and 58 are. operated between collapsed andstraightened'positions to move the movable contact between correspondingopen and closed circuit positions, by means of overcenter tension-typesprings l which arelconnected between the bightportion of a gen- 1 tion76 is-providedyof insulatingmaterial, having an enlarged base portionandan upstanding handle portion. The base portion of the handle member76 includes an aperture 77 through which alug portion 78 of the handlesupport member 72'extends. An anchoring screw 79 extends-throughthe-bightportion of the handle support member 72' andinto threadedengagement with the handle member 76. a It will be observed that. thehandle member 76.is thereby rigidly and fixedly supported on'thehandlesupporting member 72-bythe useof only a single screw. The base portionofthe'handle member '76 is normally covered by a sliding shield ofinsulating material as shown particularly in FIGURE 2, which is adaptedto close the handle opening in the top portion of the circuit breakercasing in all positions of the operating handle.

The operation of the circuit breaker mechanism will In the off positioninisolid lines andin the on position in'dottcd lines. 'It'will beobserved that as the handle 76 is-moved from the off and toward the onposition, the tension springs 71 pass overcenter across the line ofcenters of the pins 59 and 73, and cause the upper toggle link-57 torotate in a counterclockwise direction about its pivotal support 59 onthe releasable trip member .54, thereby straighteningthetogglelinkageand moving the contact arm to closed circuit position. The.togglevlink 57 is'stopped in itsforward movement by engagement with apin" 80 carried by the releasable trip member 54.

When the releasable trip Ymember. 54 is released by I action of acurrentresponsive device as described above, the action of the tension springs71 is such as to draw the toggle knee pivot pin 73 of the togglelinkage=up- .wardly toward theihan'dle, thereby rotating the trip member54 clockwise about its pivotal support 55 and moving the contactv armsto openposition as showniin FlGURE 4. The movement of the releasabletripmember 54 clockwise islimited bythe engagement of the pin 80 with the inthe. opening action :by:starting a collapsing action, of the togglelinkage.

. As the pin 73 moves upwardly under-the nfluenceof the springs 71, italso movestoward theleft and :thereby changes the line of action ofthesprings 71 with respect to thepivot point 75 of the handle supportmember 72 and causes the handle support member72 to movecounterclockwise. The counterclockwise movement of thelhandle supportmember 72 is limited by the engagement of pin 81 carried by the handlesupport member 72' with the edge portion 82 of the releasable tripmember 54, in which position, the parts cometorest. Overtravel orwhipping of the contact-carrying portions 17 .of the two outside polesis restricted by the provision of abutments 17a molded integral with thecasing cover 11.

r In order to reset andreclo'sethe circuit breaker mechanism, the handleisgmoved manually-toward'the otf positionduri-ng which movement the pin.81.carried by the handle support member 72, engagesthe edge portionof'the' releasable trip member 54and likewiserotates it inascounterclockwise direction untilthelatch end-portion 61 thereof. isbelow the latch retaining portion-:62 of the intermediate latch member.63. Slight further counterclockwise-movement. of the handle 72 causes;the

knee portion of the toggle linkage, 57 andz-58 to engage,

.62 overlies the latch portion 61 of the releasable trip member. Thelatch member 66 is then freeto rotate slightly counterclockwise'underthe bias .of latchreturn spring 84 to: againretain the latch portion 62in latching position. The breakersmay thereafterbe returned to the onposition. I

It will beobserved that because ofdimensional limitaitions,'thereleasabletrip member 54 'isnot long enough, nor is sufiicient. counterrotation of the handle-member 72 possibletocauseresetting of the latchmember .63 ibymeans' of the endportion ofthentripmernber. -Instead, useis made of the, knee portion oftheitoggle linkage-toperform thisfunction, thus .makingpossibleaan extremely compact mechanism.

The side plate members 50 and 51 of -the mechanism areretained on theinsulating base 10 by suitablemeans .such as by screws =86which enterinto lanced out threaded portions87of the side plates. It .will beobserved that the positioning of the side plates with respect to thein-.sulating base is determined by the lower edge of the side [framesyandthatino bending-over is necessary to attach these parts. This aifordsanimportantadvantage, since the dimensions which are determined bystamping out of apiece of metalin the flat condition can be extremely Iclosely control1ed,-while those involved or affected by these parts isassured. This assures also that there will beno tilting or cockingof themechanism, which would be ,very undesirable because of the limitedspaceinvolved, and also makes it possible touse only a single joining .member-to attach the two-side plate portionsof the mechanism together, i.e.,pin 55,.it'being observed that none of the other pins which arepositioned betweenthe sides of the casing are headed-over or includeretaining elements.

The contact cross arm 22 is pivotally supported by being inserted intoopenend notches 88 in the side plates 50 and 51. This restrains thecontact cross arm from movementvertically toward and away from the backwall of the circuit breaker casing. The contact shaft cross arm 22 isretained from movement horizontally, that is, parallel to the backwall:of-the circuit breaker by engagementof portions thereof withcorresponding 7 vertical bearing portions provided integral with theinsulating casing. Such bearing surfaces are shown, for example, inFIGURE '1 at 89 in the outer side wall of the casing and also at 89 inthe insulating barrier portion between the two adjacent recesses. Thisconstruction greatly simplifies the assembly of the mechanism and thecircuit breaker, since it is only necessary to insert the contact crossarm in the notches 87 of the side mechanism plates and then to insertthe assembled mechanism into the insulating base of the circuit breakerand to anchor it therein. Thereafter, the contact cross arm is closelyretained from movement in all directions by the various bearing surfacesmentioned.

The common trip bar 66 is pivotally supported upon a shaft 67 which isprovided With a pair of intermediate noncircular portions which areadapted to fit into the slots 90 in the mechanism side plates and thento be rotated into final position in the enlarged portion of the slots.Thereafter it cannot-be removed from its position since it is notpossible to rotate the trip member sufliciently after insertion in thecircuit breaker casing.

Referring to FIGURE 2, it will be observed that the parts comprising thewinding 27 of the magnetic trip and the connecting strap 26 connectingto the braid 25 are connected together as described above by the screw45. Although this screw serves primarily to bolt these conductivemembers directly together to establish an electrical connection, it alsoserves to maintain and anchor this end of the magnet winding in place.Thus the conductive strap 26 includes portions overlying portions of theinsulating casing, namely, at 92 and an intermediate portion underlyinga portion of the insulating casing at 94. This is made possible byproviding an opening 92a in the bottom of the casing so that the portion94 of the casing constitutes a bridge-like portion raised above thegeneral level of the bottom of the insulating casing and under which thestrap 26 may be extended. When the parts 26 and 27 are connectedtogether by the screws 45, it will be observed that the parts are allmaintained in position as well as being connected together. Thismounting between the screws 45 and 30 also serves to retain the entiremagnetic trip assembly in position comprlsing the core 28 and itsassociated pole pieces 34.

Referring particularly to FIGURES 1 and 2, it will be observed that thecircuit breaker casing is provided with extended end portions of thecover 11 thereof which extend over the line and load terminals 15 and33. Generally square access openings 93 are provided in these extendedportions in order to permit the insertion of a screwdriver to tightenthe terminals 15 and 33. In order to make possible the ready closure ofthe openings 93, however, lip portions 95 are provided at each of twoopposed sides of the apertures 93 and projections 96, extending inwardlyfrom the other two opposed sides of the aperture. A closure member 97,conforming in outline generally to the apertures 93 and of relativelythin resil-. rent insulating material, is then snapped into position ineach of the apertures 93 so as to assume the trapped position shown inFIGURE 2. It has been found that these closure members are securelyretained by this construction and that it is virtually impossible toremove them from the top surface of the breaker.

Referring to FIGURE 10, there is also provided, in accordance with theinvention, an auxiliary switch 100 which is rigidly attached to asupporting plate 101. The supporting plate 101 is retained in positionby portions thereof which extend into slots 192 in opposed side Walls ofthe circuit breaker chamber 12. The switch 100 includes a reciprocatingtype actuator 103. The barrier portion 104 of the insulating cover 11 isprovided with anaperture 105 therein in alignment with the actuator 103,and a sliding actuator extension portion 103 is slidably trapped in theaperture 105, and includes a cam surface inner end which is normallyurged into engagement with a side portion of the insulating handlemember 76..

The insulating handle member 76 has its major portion thereofdimensioned so that when the handle is in either the on or the offposition, the actuator of theswitch is held in an inactive position. Theinsulating handle member 76 is, however, also provided with a recess 106in the side wall thereof substantially half way between the ends thereofwhich is disposed to be in alignment with the actuator 103 when thehandle is inthe tripped position as indicated in FIGURES 2 and 4. Whenthe handle is in this position, the extensions 103a extends into therecess 106 allowing the switch 100 to assume its closed position,thereby giving a remote indication of the tripped condition of thecircuit breaker. By means of this construction, it is unnecessary to addany particular actuating portion to the circuit breaker mechanism inorder to actuate such a trip indicating switch, or to have engagementwith the releasable trip member 54. The handle 76 is also provided witha recess 106 in both sides thereof so that the trip indicating switchmay be mounted in either of the outer chambers 12 as desired. For thepurpose of facilitating the introduction of conductors to and from theswitch 100 or similar device, knockout portions 10a (see FIG. 1) areprovided in the bottom wall of the casing base 10, between the centralchamber 12 and each of the two outside chambers.

In FIGURES 7-9 I have shown modifications of the trip or currentresponsive mechanism. In FIGURE 7 there is shown a mechanism whichincludes a magnetic trip having a winding comprising three completeturns. In FIGURE 8 there is shown a magnetic trip having a windingcomprising only a single turn, while in FIGURE 9 there is shown amagnetic trip having a Winding comprising two complete turns.

In FIGURE 6 there is shown a modification of the invention which isadapted for use in a single-pole circuit breaker. In this form of theinvention, the intermediate latch member 63 is omitted and instead thelatch member 110 is pivotally supported on a pin 111 in the side framemembers of the mechanism and is biased by a tension type spring 112 in acounterclockwise direction. The latch member 110 includes anintermediate lanced-out latch portion 113 which engages the latching end61 of the releasable trip member 54. Upon deflection of the bimetallicstrip 114, the screw 115 carried thereby engages the upper end of thetrip member of the latch 110 and rotates it clockwise, withdrawing thelatch 113 from the tripped member 54 and causing tripping. A magnetictrip member is also provided, including a generally U-shaped field piece116 rigidly attached to the bimetallic strip 114 and adapted to attractthe lower end of the latch member 110 as an armature, to likewise causetripping. In order to provide a bypassing circuit to protect thebimetallic strip 114 in a manner similar to that described above, a pairof shorting contacts 117 are provided, one of which is carried ininsulated relation on the latch member 110 and connected by a flexibleconductor or braid, not shown, to the upper end of the bimetallic strip114. The other of the shorting contacts 117 is carried by a resilientconductive strip member 118 which is connected to the conductive braid119 leading to the movable contact.

While I have shown only specific forms of my invention, it will bereadily appreciated that many modifications thereof may be made by thoseskilled in the art, and I therefore intend by the appended claims tocover all such modifications as fall within the true spirit and scope ofthe invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. An electric circuit breaker comprising at least one stationarycontact, at least one relatively movable contact movable into and out ofengagement with said stationary contact, operating mechanism foroperating said relatively movable contacts comprising a pair ofgenerally planar opposed side plates, said side plates having opposedportions thereof return-bent toward each other to provide a pair ofgenerally U-shaped portions in juxtaposed relation,

a releasable trip member pivotally supported between said juxtaposedreturn-bent portions of said side plates, and a pivot pin passingthrough said return-bent portions and said trip member and retainingsaid side plates together and acting as a pivot pin for said tripmember.

2. An electric circuit breaker comprising an insulating casing, at leastone relatively stationary contact supported in said insulating casing,at least one relatively movable contact supported in said insulatingcasing and movable into and out of engagement with said stationarycontact, operating mechanism for operating said relative- 1y movablecontact comprising a pair of opposed generally planar metallic sideplates supported in spaced apart side-by-side alignment in said casing,a pivotally sup ported shaft extending between said opposed side plates,a contact arm rigidly attached to said shaft and adapted to move saidmovable contact, a manually operable handle member pivotally supportedon said opposed side plates, said opposed side plates having opposedforward edge portions thereof return-bent to provide two juxtaposedgeneraly u-shaped portions, said return-bent portions extendinginclosely spaced side-by-side relation, a pair of aligned apertures insaid return-bent portions of said side plates, a releasable trip memberextending between said return-bent portions and having an aperture inalignment with said apertures therein, a pivot pin extending throughsaid return-bent portions and through said trip member, said pivot pinhaving its opposite end beaded-over to retain said side plates together,a pair of toggle links extending between said releasable trip member andsaid movable contact member, and spring means extending between saidmanualy operable handle member s and the knee point of said togglelinkage for operating said toggle linkage between off and on positions.

3. An electric circuit breaker comprising aninsulating I casing, atleast one relatively sationary contact supported in said insulatingcasing, at least one relatively movable contact supported in saidinsulating casing and movable into and out of engagement with saidstationary contact, operating mechanism for operating said relativelymovable contact comprising a pair of opposed generally planar metallicside plates supported in spaced apart side-byside alignment in saidcasing, a pivotally supported shaft extending between said opposed sideplates, a contact arm rigidly attached to said shaft and adapted to movesaid movable contact, a manually operable handle member pivotallysupported on said opposed side plates, said opposed side plates havingopposed forward edge portions thereof return-bent to provide twojuxtaposed generally U-shaped portions, said return-bent portionsextending in closely spaced side-by-side relation, a pair of alignedapertures in said return-bent portions of said side plates, a releasabletrip member extending between said returnbent portions and having anaperture in alignment with said apertures therein, a pivot pin extendingthrough said return-bent portions and through said trip member, saidpivot pin having its opposite ends headed-over to retain said sideplates together, a pair of toggle links extending between saidreleasable trip member and said movable contact member, and spring meansextending between said manually operable handle member and the kneepoint of said toggle linkage for operating said toggle linkage betweenoff and on positions, said returnbent portions of said side platesincluding aligned shoulder portions, and said releasable trip memberincluding a pair of opposed aligned projections adapted to engage saidshoulder portions upon releasing movement of said releasable member toprovide a stop for such releasing movement. 0

4. An electric circuit breaker as set forth in claim 3 whereinsaidprojections carried by said releasable trip member are positioned toserve as stops to prevent overtravel of said toggle linkage and alsoserve to initiate c01- lapsing movement of said toggle linkage uponrelease of said releasable member.

5. An electric circuit breaker comprising an insulating casing, arelatively stationary contact mounted in said insulating casing, arelatively movable contact supported in said insulating casing formovement into and out of engagement with said stationary contact,operating mechanism for operating said relatively stationary contactcomprising a pair of opposed generally planar side plates of metallicmaterial, said side plates having the lower edge portions thereof inengagement with said bottom surface of said insulating casing, said sideplates having portions thereof lanced out and deformed to opposite sidesof said plane of said plate and tapped to receive retaining screws,openings in said insulating base in alignment with said tapped portionsof said plate, and retaining screws pass- References Cited in the fileof this patent UNITED STATES PATENTS Dor-fman Sept. 1, 1942 Kiesel et a1Oct. 13, 1959

